Abstract

Polystyrene (PS) is a common microplastic can have toxic effects on the anaerobic digestion system of sludge by affecting the secretion of organic matter and volatile fatty acid, the activity of related enzymes, and the structure of microbial communities. Magnetite is a common conductive magnetic material can enhance anaerobic digestion of sludge. For the purpose to investigate the improvement of magnetite to an anaerobic digestion system inhibited by high quantity of PS microplastics, for anaerobic digestion of sludge were built and run with different conditions. The results demonstrated that high concentration microplastic stress of 300 particles/gTS initially inhibit VFAs synthesis, followed by further inhibition of protease and coenzyme F420 functions, ultimately leading to the accumulation of propionic acid/butyric acid and inhibiting anaerobic digestion for methane production, and an appropriate amount of magnetite (1 g/L) can effectively alleviate the methane production inhibition induced by microplastics (from 6.41 mlCH 4 /gVS∙d to 9.24 mlCH 4 /gVS∙d) through enhanced butyrate kinase activity and coupled with selective enrichment of Methanospirillum to optimize VFAs utilization. The microbial community reorganization supplemented by magnetite increased bacterial abundance and promoted the surface oxidation and fragmentation degree of PS. The findings reveal the addition of magnetite can alleviate the toxic effects of PS particles on the system and enhance its running performance.